With respect to an electrolytic etching method and apparatus, as publically known typical examples wherein a metal surface is electrolytically etched with an electrolytic etching liquid locally retained adjacent to an electrode, Patent Documents 1 and 2 are enumerated.
Patent Document 1 relates to a method of polishing a metal surface, characterized in that an etching liquid is retained in an area surrounded by an ionic-conductive membrane.
Patent Document 2 relates to a decontamination method for removing an oxide film including a radionuclide, and the like, which adhere to the metal surface of an apparatus or machinery and tools in a nuclear power plant, characterized in that an electrolyte film is brought into contact with the metal surface, and an electrode coming into contact with the electrolyte film is energized, whereby the oxide film and the like are removed.